Specialty centers may confer improved outcomes for long QT syndrome

August 4, 2017

Michael J. Ackerman

Patients with long QT syndrome who were treated at a single specialized center had reduced rates of cardiac events, according to research published in the Journal of the American College of Cardiology.

“Although long QT syndrome is a potentially lethal syndrome, when it is recognized and treated, sudden death should almost never happen,” Michael J. Ackerman, MD, PhD, director of the Long QT Syndrome/Genetic Heart Rhythm Clinic at the Mayo Clinic in Rochester, Minnesota, said in a press release. “The expectation needs to shift from merely preventing sudden death to enabling these patients and their families to live and thrive despite the diagnosis.”

Contemporary treatment strategies

Researchers conducted a retrospective review of data from 606 patients (median age at diagnosis, 15 years; 59% women) with long QT syndrome who were treated at a single center from 1999 to 2015. Most patients were positive for genetic testing (98%): 287 patients had long QT syndrome-1, 204 patients had long QT syndrome-2 and 56 patients had long QT syndrome-3. Median follow-up was 6.7 years.

Patients were considered symptomatic if a long QT syndrome-related cardiac symptom, including arrhythmogenic seizure or syncope, fetal arrhythmia or cardiac arrest, occurred prior to diagnosis.

The primary evaluated outcome was incidence of long QT syndrome-related breakthrough cardiac event, which included seizure, arrhythmogenic syncope, sudden cardiac death, aborted cardiac arrest or an appropriate ventricular fibrillation-termination implantable cardioverter defibrillator shock after an initial evaluation at the center.

Twenty-seven percent of patients were symptomatic before their first evaluation at the clinic. The median age at first long QT syndrome event was 12 years.

Treatment strategies varied among the group: 58% of patients were taking beta-blockers, 4% had ICDs, 3% had left cardiac sympathetic denervation, 27% had combined therapies and 8% were intentionally not treated.

Breakthrough cardiac events

Most patients (92%) did not have a long QT syndrome-related breakthrough cardiac event during follow-up. Two percent of patients who were previously asymptomatic had one breakthrough cardiac event, and 25% of patients who were previously asymptomatic experienced one or more breakthrough cardiac events.

About 0.3% of patients from the entire cohort with two or more breakthrough cardiac events died. Fewer than 0.5% of patients received heart transplants during 4,000 years of treated follow-up.

“Although mortality is rare (< 1% of patients in over 4,000 patient-years) and outcomes have improved in comparison with previous studies, nearly one in four symptomatic patients still experienced at least one nonlethal [breakthrough cardiac event],” Ram K. Rohatgi, MD, from the department of pediatric and adolescent medicine at the Mayo Clinic in Rochester, Minnesota, and colleagues wrote. “This indicates that there is still need for improved risk stratification and optimization of their treatment program.”

Peter J. Schwartz, MD, head of the Center for Cardiac Arrhythmias of Genetic Origin and director of the Cardiovascular Genetics Laboratory at the IRCCS Istituto Auxologico Italiano in Milan, and colleagues discussed the evolution in long QT syndrome management in a related editorial.

“[These mortality data] mean that, when treated well and by experts, [long QT syndrome] should no longer be considered a disease with a high risk for sudden death,” Schwartz and colleagues wrote. “This important result does not come by chance; in our opinion, besides the greater accuracy in risk stratification provided by genetic analysis, an important role is played by a very experienced team with a uniform approach, and especially by the fact that 80% of the Mayo patients return every 1 to 2 years and that 95% of our patients return every year (even after 40 years) for a complete visit and assessment.” – by Darlene Dobkowski

Disclosures:This study was supported by the Mayo Clinic Windland Smith Rice Comprehensive Sudden Cardiac Death Program. Ackerman reports receiving royalties until 2016 from Transgenomic; a licensing agreement with AliveCor; and consulting for Boston Scientific, Gilead Sciences, Invitae, Medtronic, MyoKardia and St. Jude Medical. Rohatgi and Schwartz report no relevant financial disclosures. Please see the full study for a list of the other authors’ relevant financial disclosures.

Michael J. Ackerman

Patients with long QT syndrome who were treated at a single specialized center had reduced rates of cardiac events, according to research published in the Journal of the American College of Cardiology.

“Although long QT syndrome is a potentially lethal syndrome, when it is recognized and treated, sudden death should almost never happen,” Michael J. Ackerman, MD, PhD, director of the Long QT Syndrome/Genetic Heart Rhythm Clinic at the Mayo Clinic in Rochester, Minnesota, said in a press release. “The expectation needs to shift from merely preventing sudden death to enabling these patients and their families to live and thrive despite the diagnosis.”

Contemporary treatment strategies

Researchers conducted a retrospective review of data from 606 patients (median age at diagnosis, 15 years; 59% women) with long QT syndrome who were treated at a single center from 1999 to 2015. Most patients were positive for genetic testing (98%): 287 patients had long QT syndrome-1, 204 patients had long QT syndrome-2 and 56 patients had long QT syndrome-3. Median follow-up was 6.7 years.

Patients were considered symptomatic if a long QT syndrome-related cardiac symptom, including arrhythmogenic seizure or syncope, fetal arrhythmia or cardiac arrest, occurred prior to diagnosis.

The primary evaluated outcome was incidence of long QT syndrome-related breakthrough cardiac event, which included seizure, arrhythmogenic syncope, sudden cardiac death, aborted cardiac arrest or an appropriate ventricular fibrillation-termination implantable cardioverter defibrillator shock after an initial evaluation at the center.

Twenty-seven percent of patients were symptomatic before their first evaluation at the clinic. The median age at first long QT syndrome event was 12 years.

Treatment strategies varied among the group: 58% of patients were taking beta-blockers, 4% had ICDs, 3% had left cardiac sympathetic denervation, 27% had combined therapies and 8% were intentionally not treated.

Breakthrough cardiac events

Most patients (92%) did not have a long QT syndrome-related breakthrough cardiac event during follow-up. Two percent of patients who were previously asymptomatic had one breakthrough cardiac event, and 25% of patients who were previously asymptomatic experienced one or more breakthrough cardiac events.

About 0.3% of patients from the entire cohort with two or more breakthrough cardiac events died. Fewer than 0.5% of patients received heart transplants during 4,000 years of treated follow-up.

“Although mortality is rare (< 1% of patients in over 4,000 patient-years) and outcomes have improved in comparison with previous studies, nearly one in four symptomatic patients still experienced at least one nonlethal [breakthrough cardiac event],” Ram K. Rohatgi, MD, from the department of pediatric and adolescent medicine at the Mayo Clinic in Rochester, Minnesota, and colleagues wrote. “This indicates that there is still need for improved risk stratification and optimization of their treatment program.”

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Peter J. Schwartz, MD, head of the Center for Cardiac Arrhythmias of Genetic Origin and director of the Cardiovascular Genetics Laboratory at the IRCCS Istituto Auxologico Italiano in Milan, and colleagues discussed the evolution in long QT syndrome management in a related editorial.

“[These mortality data] mean that, when treated well and by experts, [long QT syndrome] should no longer be considered a disease with a high risk for sudden death,” Schwartz and colleagues wrote. “This important result does not come by chance; in our opinion, besides the greater accuracy in risk stratification provided by genetic analysis, an important role is played by a very experienced team with a uniform approach, and especially by the fact that 80% of the Mayo patients return every 1 to 2 years and that 95% of our patients return every year (even after 40 years) for a complete visit and assessment.” – by Darlene Dobkowski

Disclosures:This study was supported by the Mayo Clinic Windland Smith Rice Comprehensive Sudden Cardiac Death Program. Ackerman reports receiving royalties until 2016 from Transgenomic; a licensing agreement with AliveCor; and consulting for Boston Scientific, Gilead Sciences, Invitae, Medtronic, MyoKardia and St. Jude Medical. Rohatgi and Schwartz report no relevant financial disclosures. Please see the full study for a list of the other authors’ relevant financial disclosures.